Method of manufacture of plastic bags and the improved bags resulting therefrom

ABSTRACT

A multi-layer plastic bag with a valvular opening is formed by providing a multi-layer plastic tube, closing the bottom end of the tube by folding in end portions of opposite major walls over one another thereby forming pyramidal projections which are then folded over the folded end portions of the major walls whereupon the folded portions are secured by electronic stitching; and closing the top end of the tube in similar manner but with a valvular opening at one end of the top formed by slitting the tube wall to provide a flap, introducing a U-shaped band between upper end portions of opposite side walls of the tube, folding the flap over the bottom of the U-shaped band, folding the side portions of the U-shaped band down with side portions of the tube, and securing the folded portions by electronically stitching.

United States Patent Siekierski [54] METHOD OF MANUFACTURE OF PLASTIC BAGS AND THE IMPROVED BAGS RESULTING THEREFROM [72] Inventor: Jacques Siekierski, Sao Paulo, Brazil [7 3] Assignee: ITAP S/A-Industria Tecnica De Artefatos Plasticos Rua Prof. Celestino Bourroul, Sao Paulo, Brazil [22] Filed: June 18, 1970 [21] Appl. No.: 47,543

[52] U.S. Cl ..229/58, 229/625 [51] Int. Cl. ..B65d 33/16 [58] Field of Search ..229/55, 57, 58, 62, 62.5

[56] References Cited UNITED STATES PATENTS 3,065,899 11/1962 Meansetal ..229/62.5 3,494,459 2/1970 Titchenal ..229/55X FOREIGN PATENTS OR APPLICATIONS 793,129 8/1968 Canada ..229/58 [151 3,680,769 Aug. 1,1972

Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Michael Y. Mar Attorney-Robert E. Burns and Emmanuel J. Lobato [57] ABSTRACT A multi-layer plasticbag with a valvular opening is formed by providing a multi-layer plastic tube, closing the bottom end of the tube by folding in end portions of opposite major walls' over one another thereby forming pyramidal projections which are then folded over the folded end portions of the major walls whereupon the folded portions are secured by electronic stitching; and closing the top end of the tube in similar manner but with a valvular opening at one end of the top formed by slitting the tube wall to provide a flap, introducing a U-shaped band between upper end portions of opposite side walls of the tube, folding the flap over the bottom of the U-shaped band, folding the side portions of the U-shaped band down with side portions of the tube, and securing the folded portions by electronically stitching.

6 Claim, 7 Drawing Figures METHOD OF MANUFACTURE OF PLASTIC BAGS AND THE IMPROVED BAGS RESULTING THEREFROM It is an object of this invention to provide an im-. proved method for manufacturing bags made out of plastic sheets which are hermetically sealed at the bottom and having a valvular opening at the top for the introduction and the expulsion of the liquid or solid contents.

It is another object of this invention to provide an improved plastic non-rigid container whose reinforced structure prevents leakages and ruptures so as to become a reliable substitute for the rigid vessels heretofore used to carry out and protect liquid substances and solid materials, both powdered or granular.

Yet another object of this invention is to provide an improved method for manufacturing heavy duty plastic bags comprising a succession of folding and sealing steps that allow a speeding-up of production with the economical advantage of a reduced cost.

As it is known by those skilled in the art, the production of laminated plastic sheets and films, despite the technological development of the plastic industry, suffers from the difficulty in obtaining products homogeneous in thickness, consistency and strength which means that is usual to find zones of reduced strength that shortens the life period of the one-sheet bags heretofore known.

To overcome such drawbacks the improved plastic sacks of this invention are composed of a multi-layered body constituted by two, three or more lower priced superimposed plastic sheets, of reduced thickness, in lieu of a sole thicker sheet to obtain a homogeneously strengthened bag.

An advantage flowing from the use of a multi-layered structure is that a charge and discharge opening may be more easilyobtained'as will be disclosed hereinafter.

The invention will be better understood through the attached drawings which illustrate a preferred embodiment of the invention as follows:

. FIG. 1 is a perspective view of the tubular body of the bag, according to the invention, before the folding of its top and bottom openings; v

FIG. 2 is a perspective view showing an intermediate step of the folding phase of the bottom of the bag;

FIG. 3 is a perspective view of the bottom of the bag duly closed and sealed;

FIG. 4 is a perspective view illustrating the first step of the folding operation of the mouth of the bag;

FIG. 5 is a perspective view of the bag after an intermediate step of the folding operation FIG. 6 is a perspective view of the top of the bag duly folded; and

FIG. 7 is a perspective view of the finished ready-tofill bag.

In accordance with the operative sequence for closing the bottom portion 4 of the bag shown in FIGS. 1, 2 and 3 the tubular body 1 of the bag is initially flattened at one end into an elliptic cross section having two opposite walls 2, 3 bent one over the other along the greater axis of the elliptical base thereby forming a longitudinal reinforced zone opposite pyramidal projections 5 and 6. The projections 5 and 6 are then bent inwardly' on the axis a and b over the base (FIG. 2) afterwhich the folded plastic sheets are electronically sewn together by means of a double-seam welding 7 extending centrally along the base 4 and being triangularly branched at its end following the folded edges of the projections 5, 6.

FIGS. 4 to 7 illustrate the folding operation of the top portion 9 and the obtention of the valvular charge-anddischarge mouth 15 of the bag.

FIG. 4 shows the free edges of the opposite walls 10, 11 having a lateral flap 12 cut from the walls. A band 13 of colored plastic is introduced within the walls 10, ll slightly spaced from the flap 12. The flaps 12 is then bent inwardly over the bottom of the band 13 and the folding of the top portion is then carried out in 9 the same way as described for the bottom portion 4.

As a result of the appropriate folding of the flap l2 and of the walls 10, 11, the free edges of the walls 10, 11 and the said flap 12 are suitably bent around the band 13 thereby forming a reinforced pocket surrounding an opening mouth 15 (FIG. 6).

Of course, while the mouth 15 is obtained in the left side of the top portion 9, in the right side a pyramidal projection 14 is shaped and folded in the same way as the projection 5, and 6 in the bottom portion 4.

The resulting plaits are fixed and sealed by means of a double-seam welding 16 extending longitudinally onto the central zone of the top portion 9 having a triangular branching 17 accompanying the foldings of the projection 14 and, an inverted U-shaped configuration 18 along the border and the lateral sides of the mouth 15 (FIG. 7).

The multi-layer structure of the improved bag of this invention is shown in the broken views in FIGS. 5, 7 and 4 where the one-sheet 19 construction, the twolayer 19, 20 construction, and the three-layer 19, 20,21 construction are respectively illustrated. It is obvious that the shape of the bag and the number of layers of plastic sheets employed to embody the same can change at will without departing from the scope of the invention as defined in the following claims and shown in the attached drawings.

I claim:

1. An improved method of manufacture of leakproof plastic bags of the general kind having a valvular upper opening for the charging and discharging of, liquid or solid contents, comprising: providing a hollow openended plastic tubular multi-layer body having a major axis and a minor axis and flattened into an elliptic shape whose open ends are closed and sealed as top and bottom bases by partially overlapping the free edges of the opposite walls, along the major axis of the base, forming a central reinforced cone and generating at the extremities two opposite pseudo-pyramidal projections which are convergently bent over the base forming triangular folds where they are welded by means of electronic welding and forming a central double-seam branching at opposite ends following the folded edges of the said projections.

2. The method as claimed in claim 1 in which the top base of the bag is provided with a valvular opening which is obtained through the steps of cutting a lateral flap from the opposite free walls of the enclosed end, introducing between the said walls, slightly apart from the said flap, a U-shaped band of colored plastic material bending thereafter the said flap over the bottom of the U band and of partially overlapping the free edges of said walls forming a pocket from the consequent folding of said band and generating a pseudopyramidal projection at the opposite side which is then bent inwardly forming a triangular fold and finally fixing all of the folds by electronic welding of a doubleseam extending longitudinally on the centerline of the base and branching at right into a triangle following the folded edges of said projection and into an inverted U" at left, along the border.

3. A multi-layer bag manufactured in accordance with the method claimed in claim 1 two or more superimposed plastic sheets of reduced thickness, fixed and bonded together forming a thicker wall with the desired strength, having the bottom base hermetically sealed with a double-seam of electronic welding extending longitudinally onto a central reinforced zone obtained by the partial overlapping of the walls of the bag and branching at ends into a triangle following the folded edges of the opposite pyramidal projections bent over the base, and provided in the upper base with a valvular opening, at the opposite side to a pyramidal projection bent over the said bases, said opening being provided by a colored plastic band fitted into the walls of the bag, before the partial overlapping of said walls and by a lateral flap cut from said walls, folded over the bottom of the said band, the whole folds and edges being fixed and sealed by a double-seam electronic weld.

4. A method of manufacturing plastic bags comprising: providing a hollow open-ended plastic body having an elongated cross-sectional configuration which has a major axis and a minor axis; closing one open end of the hollow plastic body by partially overlapping opposed edge portions thereof along said major axis thereby forming a seam along the overlapped portion; sealing the closed one end by heat-welding said seam; placing a reinforcing insert in a portion of the other open end of said hollow plastic body; closing said other open end of said hollow plastic body while bending said reinforcing insert into an arcuate shape which provides communication between the interior and exterior of said hollow plastic body by partially overlapping opposed edge portions thereof along said major axis thereby forming another seam along the overlapped portion; and sealing the closed other end by heat-welding said another seam; whereby a plastic bag having a material opening is formed.

5. A method according to claim 4; wherein said step of closing said other open end comprises forming one minor edge portion of said other open end into a flap, bending said flap inwardly over a portion of said reinforcing insert, and then overlapping opposed major edge portions of the other open end over the flap to effect bending of said reinforcing insert into a hollow configuration.

6. A method according to claim 5; wherein said sealing steps comprise electronically sewing said seams. 

1. An improved method of manufacture of leakproof plastic bags of the general kind having a valvular upper opening for the charging and discharging of, liquid or solid contents, comprising: providing a hollow open-ended plastic tubular multilayer body having a major axis and a minor axis and flattened into an elliptic shape whose open ends are closed and sealed as top and bottom bases by partially overlapping the free edges of the opposite walls, along the major axis of the base, forming a central reinforced cone and generating at the extremities two opposite pseudo-pyramidal projections which are convergently bent over the base forming triangular folds where they are welded by means of electronic welding and forming a central double-seam branching at opposite ends following the folded edges of the said projections.
 2. The method as claimed in claim 1 in which the top base of the bag is provided with a valvular opening which is obtained through the steps of cutting a lateral flap from the opposite free walls of the enclosed end, introducing between the said walls, slightly apart from the said flap, a U-shaped band of colored plastic material bending thereafter the said flap over the bottom of the ''''U'''' band and of partially overlapping the free edges of said walls forming a pocket from the consequent folding of said band and generating a pseudo-pyramidal projection at the opposite side which is then bent inwardly forming A triangular fold and finally fixing all of the folds by electronic welding of a double-seam extending longitudinally on the centerline of the base and branching at right into a triangle following the folded edges of said projection and into an inverted ''''U'''' at left, along the border.
 3. A multi-layer bag manufactured in accordance with the method claimed in claim 1 two or more superimposed plastic sheets of reduced thickness, fixed and bonded together forming a thicker wall with the desired strength, having the bottom base hermetically sealed with a double-seam of electronic welding extending longitudinally onto a central reinforced zone obtained by the partial overlapping of the walls of the bag and branching at ends into a triangle following the folded edges of the opposite pyramidal projections bent over the base, and provided in the upper base with a valvular opening, at the opposite side to a pyramidal projection bent over the said bases, said opening being provided by a colored plastic band fitted into the walls of the bag, before the partial overlapping of said walls and by a lateral flap cut from said walls, folded over the bottom of the said band, the whole folds and edges being fixed and sealed by a double-seam electronic weld.
 4. A method of manufacturing plastic bags comprising: providing a hollow open-ended plastic body having an elongated cross-sectional configuration which has a major axis and a minor axis; closing one open end of the hollow plastic body by partially overlapping opposed edge portions thereof along said major axis thereby forming a seam along the overlapped portion; sealing the closed one end by heat-welding said seam; placing a reinforcing insert in a portion of the other open end of said hollow plastic body; closing said other open end of said hollow plastic body while bending said reinforcing insert into an arcuate shape which provides communication between the interior and exterior of said hollow plastic body by partially overlapping opposed edge portions thereof along said major axis thereby forming another seam along the overlapped portion; and sealing the closed other end by heat-welding said another seam; whereby a plastic bag having a material opening is formed.
 5. A method according to claim 4; wherein said step of closing said other open end comprises forming one minor edge portion of said other open end into a flap, bending said flap inwardly over a portion of said reinforcing insert, and then overlapping opposed major edge portions of the other open end over the flap to effect bending of said reinforcing insert into a hollow configuration.
 6. A method according to claim 5; wherein said sealing steps comprise electronically sewing said seams. 